Manual resuscitators for use with patients either unable to breathe on their own or needing assistance are well known in the prior art. An example of a prior art resuscitator is described in U.S. Pat. No. 4,774,941 to Cook. A typical prior art resuscitator comprises a resuscitator bag for mechanically forcing oxygen or air into the patient, a regulator for controlling the flow of inhalation and exhalation gasses, and a means for connecting the resuscitator to the patient such as a facemask or intubation tube.
A serious problem in the resuscitation of patients is the inability to determine whether the patient is respirating. It is difficult for the medical professional using the resuscitator to determine whether the patient is receiving an adequate flow of oxygen. For example, something may be blocking the patient's trachea preventing oxygen air exchange or, in the case of an endotrachial tube, the tube may be inserted into the patient's esophagus. Therefore, a need has arisen for an efficient and economical way of determining whether the patient being treated with a resuscitator is actually receiving oxygen.
One way of determining whether a patient is receiving oxygen is to detect the presence of CO.sub.2 in the exhalation gasses. The normal atmospheric concentration of CO.sub.2 is less than 0.5%. So, presence of CO.sub.2 in excess of that amount is generally a strong indication that the patient is receiving oxygen and performing some respiration. Carbon dioxide detectors using a chromogenic pH-sensitive indicator are well known in the prior art. An example of such an indicator is described in U.S. Pat. Nos. 4,728,499 and 4,994,117 to Fehder. These carbon dioxide indicators are of the type that need to be connected between the patient and the resuscitator. This limitation has numerous and significant disadvantages. First, the medical professional is required to install the device before he or she can begin resuscitating the patient. In many instances, resuscitation occurs in emergency situations making such a device unattractive to the medical professional. Second, the connection of the carbon dioxide indicator adds additional volume to the breathing circuit increasing the trapping of exhaled gasses and other material. In that instance, the patient is no longer receiving fresh oxygenated air but is rebreathing his or her own exhaled gasses. This is particularly troublesome when using resuscitators on infants whose lung capacity is much smaller than those of adults. Third, since the carbon dioxide detector requires its own housing and connector ports, the expense is significantly increased over what it would be if the detector were contained integral with the resuscitator.
Therefore, a need has arisen to combine a carbon dioxide detector in a resuscitator. This need has been long recognized by the medical profession and numerous attempts have been made to design a resuscitator that integrates a carbon dioxide detector. An example of such device is disclosed in U.S. Pat. No. 4,945,918 to Abernathy. The apparatus disclosed in the Abernathy patent suffers from some of the same disadvantages described before. In particular, the Abernathy device requires assembly by the medical professional that is both cumbersome and time consuming. Another disadvantage of the Abernathy device is that the indicator is not directly incorporated in the resuscitator and is not located in the direct breathing circuit. Another disadvantage of the Abernathy device is that by failing to place the carbon dioxide detector in the direct breathing circuit, the indicator may not be cleansed with fresh air after each resuscitation and therefore accuracy of the indicator is sacrificed. Another disadvantage of the Abernathy device is that the indicator requires a four minute period to indicate whether carbon dioxide is present. These and other disadvantages of the prior art are overcome by the device of the present invention.